Carburetor



May 26, 1953 QLSQN 2,639,907

CARBURETQR Original Filed Oct. 25, 1950 3 Sheets-Sheet l INVENTOR. [1 HM0150/! E. OLSON 'CARBURETOR May 26, 1953 3 Sheets-Sheet 2 Original FiledOct. 25, 1950 INVENTOR. HM? 0150 MMMJQ ms Arm/suns E 0 L5 0 N CARBURETORMay 26, 1953 3 Sheets-Sheet 3 Original Filed 001;. 25, 1950 IN VEN TOR.

Patented May 26, 1953 CARBURETOR Elmer Olson, Rochester, N. Y., assignorto General Motors Corporation, Detroit, Mich, a corporation of DelawareOriginal application October 25, 1950, Serial No. 192,035. Divided andthis application January 12, 1952, Serial No. 266,152

Claims. 1

This invention relates to carburetors for internal combustion engines,particularly for automotive use, and is an improvement on and quitesimilar to the carburetor disclosed and claimed in applicants copendingapplication, Serial No. 109,347, filed August 9, 1949.

At the present time certain difficulties are encountered, in thefunctioning of carburetors, which are occasioned by the highly volatilefuels now in use in the operation of automotive vehicles. Because of thehighly volatile character of the fuels in use, difficulty is caused byfuel vaporization during operation under certain conditions,particularly during idling at high temperatures. There is sufficientvaporization of fuel in the fuel supply passage which conveys fuel fromthe float chamber to the fuel inlets of the carburetor, in a carburetorof conventional design, to form vapor bubbles and these tend to adhereto the wall and build up in size until the flow of fuel is largelyblocked, when the bubble will be detached and passed on to the fuelinlets. This produces an irregularity in fuel flow and consequentirregularity in engine operation which may be sufficient even to causestalling and in any event, is objectionable. The principal object of thepresent invention is to provide means to minimize the formation ofbubbles in the fuel supply passages as far as possible and to preventthe formation of bubbles large enough to interfere materially with theregularity of fuel flow under any operating conditions.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

Fig. 1 is a vertical section through the carburetor on the line I--I ofFig. 4;

Fig. 2 is a plan view of the float chamber casting 4 with the covercasting 6 removed;

Fig. 3 is a fragmentary section on line 3-3 of Fig. 1;

Fig. 4 is a plan View of the carburetor which is shown in section inFig. 1:

Fig. 5 is a section on the line 55 of Fig. 4;

Fig. 6 is an enlarged fragmentary detail of Fig. 5;

Fig. '7 is a detail section on the line 'l-'l of Fig. 6.

Referring to Fig. 1, the carburetor includes three main castings 2, 4and 6 which are, respectively, the outlet member which is attachable tothe intake, the constant level fuel chamber which is positionedimmediately above the outlet member and the air intake member which hasformed integrally therewith a cover for the fuel chamber. The outletmember has a projecting flange 8 having holes II] for receiving theattaching bolts which secure the caburetor to the manifold in the usualway. The outlet member and the fuel chamber, the fuel chamber and theair inlet, respectively, are secured together in any suitable way,gaskets l6 being provided between the several parts to prevent leakage,as shown in Fig. 1.

Depending from the casting 6 is a small casting l8, separated from thecasting 6 by a gasket 20 and in which is provided the main fuel supplypassage 22, through which fuel passes from the fuel chamber to themixture passage 24. The latter extends centrally through all of thecastings 2, 4 and 6 and supplies combustible mixture to the manifold,the flow of such mixture being controlled by a throttle valve 26 ofconventional form, secured to a shaft 28, journaled for rotation in thewall of the outlet member 2, and manually operated by mechanism whichwill be later described.

As shown best in Fig. 1, fuel is supplied from a main source of supplyto the fuel chamber through a bore 36 in casting 6 to which the fuel isdelivered by any suitable conduit. The bore 36, at its inner end,communicates with a bushing 40, screwed into casting 6 and having apassage 42 formed therein. This passage extends from the bore 36 to aspace within the bushing in which a conventional float valve 44 ispositioned and which seats against the lower end of passage 42, so as tocut off the flow of fuel into such chamber when fuel within the fuelchamber 46 reaches a predetermined level.

The float valve is operated by a finger 48 integral with and projectingfrom a lever. 50 pivoted on rod 52 supported by lugs 54 depending fromthe cover casting 6. As shown in Fig. 2, the lever 50 is attached tofloats 56 which actuate the valve 44 by the mechanism described for thepurpose of maintaining a substantially constant fuel level in thechamber 46. A finger 58 integral with lever 50 will engage the bushing40,

if for any reason there is any extreme drop in '46 to the mixturepassage. Admission of fuel to the passage 22 is primarily controlled bythe metering plug 60. Under certain operating conditions, fuel is alsoadmitted to the passage 22 through two notches 62 formed in ahorizontally projecting portion of the casting I8, as shown in Fig. 7.These notches communicate with a passage 64 which connects with a space66. A passage 68 extends from this space to the passage 22 and the flowof fuel therethrough is controlled by the metering plug Ill which ispositioned in such passage. Flow through the passage 64 is controlled bya ball check valve 12 which is held closed under some operatingconditions by a spring 14 received within the removable plug I6 screwedinto casting I8.

Under certain operating conditions when the manifold vacuum is low, aswhen operating with open throttle and at low speed, the valve I2 isopened to admit additional'fuel thus forming a somewhat richer thannormal mixture so as to give greater power. To open valve I2 under suchconditions there is provided a piston 18 slidable in a cylinder 80formed in the wall of the casting 6, as shown in Fig. 5. When the engineis not in operation, the piston is held in its lower position by aspring 82 which exerts a greater force than the spring It. The pistonhas a rod 84 extending downwardly therefrom and provided with a reducedportion 86 which holds the valve I2 open when the piston is in the Fig.5 position. A suction passage 88 connects with the cylinder 80 above thepiston and such passage communicates with the intake passage posteriorto the throttle. The entire passage is not shown, as its constructionforms no part of this invention and is the same as that disclosed inSer. No. 109,347. Obviously, during idling and when operating withpartly open throttle and light load, the manifold vacuum is high and thepiston I8 is lifted against the pressure of spring 82 so as to close thefuel passage 64. This will result in the formation of a relatively leanmixture under these conditions, but when operating with open throttle atheavy load, the vacuum is insufficient to overcome spring 82, the pistondrops, opening passage 64 to admit additional fuel to provide the richermixture necessary to give high power.

The casting I8 in which the vertical fuel passage 22 is formed issecured to the casting 6 by the screw 90 and the two castings areseparated by a gasket to limit as far as possible the transfer of heatby conductivity to the fuel passage casting I 8, and the latter is alsoso positioned that it is completely surrounded by the fuel in chamber 46to keep the temperature of such casting as low as possible.

The fuel passage 22 communicates at its upper end with a smallersubstantially vertical passage 92 formed in the casting 6. Extendingdownwardly into the fuel passage 22 is a fuel supply tube 95 which, atits upper end, connects with a short vertical passage 96 also formed incasting 6. The two passages 92 and 96 are separated by a part of thecasting 6 indicated at 99 and both communicate with a horizontalpassagewhich is divided into two parts 94a and 94b by the verticalpartition plate I00 which is fitted in the hori-" zontal passage andlies immediately above the element 96 which separates the passages 92and 96. The tube 95 extends downwardly into the passage 22, terminatingnot far above the metering plug and conveys fuel from such passage tothe passage 96 and thence to the horizontal passage 94b on the rightside of the partition I00, as seen in Fig. 5. The main part of the fuelpassage 22 conveys fuel to the passage 92 and thence to the horizontalpassage 94a which lies to the left of the partition plate I00, as seenin Fig. 5.

The purpose of the specific form of fuel supply passage above describedis to minimize as far as possible the formation of vapor bubbles and toprevent the formation of bubbles large enough to materially interferewith the continuous flow of fuel, particularly during idling at hightemperatures. This function is assisted by providing the fuel passage 22in a member which is substantially insulated from any metallic contactwith the main housing of the carburetor and which is entirely surroundedby the fuel in chamber 46 so that the temperature of the fuel in passage22 is kept as low as possible. This, of course, aids in reducing thevaporization of fuel in the passage.

Moreover the structure of the fuel supply passage is such as to preventthe formation of large enough vapor bubbles therein to materiallyinterfere with fuel how even when the engine is idling at relativelyhigh temperatures, which is the operating condition under whichdifficulty arising from fuel vaporization is most likely to beencountered. The tube is quite small and terminates at a point near thebottom of the passage 22 at which point there is but little formation ofvapor bubbles. Therefore, few bubbles will enter the tube 95 and such asdo are necessarily very small and are carried through the tube atrelatively high velocity. Therefore, what flows through thetube is acolumn of substantially solid fuel with only a small number of verysmall bubbles therein under any operating conditions.

Although the area of the remainder of the fuel passage 22 is larger thanthe cross sectional area of the passage within the tube 95, the area ofthe passage is considerably reduced by positioning the tube therein.Therefore although there will be a larger number of bubbles formed inthe fuel which flows through that part of the passage 22 outside thetube 95 than in such tube itself, such bubbles will be carried on towardthe fuel inlets and will not, except under most extreme conditions, tendto collect and build up into a bubble of sufficient size to block thepassa e or interfere materially with the flow of fuel therethrough.Also, if under any very extreme conditions, as when idling at a veryhigh temperature, there is any building up of a bubble to sufficientsize to materially obstruct the flow either through the tube or theother part of the fuel passage, such blocking of fuel flow wouldprobably never occur in both the tube and the other part of the passageat the same time so that there will substantially never be an instantwhen the interference will be more than partial and stalling even duringidling at high temperatures, will be prevented. In other words, the fuelsupply conduit comprises two substantially parallel fuel passages inwhich fuel vaporization is minimized and blocking of both passages byvapor bubbles, even under most extreme operating conditions, issubstantially impossible.

The passage 94 is formed in a horizontal tubular portion I02 of thecasting 6 which extends entirely across the mixture passage as indicatedin Fig. 1 and the divided parts of the passage 94 terminate adjacent aslightly enlarged portion of said passage which is designated 940 inFig. l. Communicating with the right end of the passage 940 is the mainfuel inlet I04, which is integral with and extends downwardly from thecross piece I02, as shown in Fig. l. The main fuel inlet is providedwith a flow controlling member I06 which is shaped somewhat like aVenturi tube, having a restricted opening and walls fiared outwardlyfrom said opening in both directions. The main fuel inlet terminates atthe throat of a primary Venturi tube I08 which, in turn, terminates atthe throat of a larger or secondary Venturi tube I I0 formed by theinner wall of the fuel chamber casting 4. The primary Venturi tube isalso integral with this casting and supported by ribs extending from thewall of the mixture passage.

Positioned in the passage 940 is a tubular member II2 having a passageII4 therethrough for the passage of idling fuel mixture. This member isreduced in size at its right end providing a small annular space II6between it and the wall of passage 940. The latter is closed at its leftend, as seen in Fig. 1, by a plug H8 and communicates with a verticalpassage I20 formed in the Wall of casting 4, the lower end of whichconnects with a horizontal passage I22 which leads to a vertical passageI24 formed in the wall of casting 2. This passage connects with twoorifices on opposite sides of the throttle valve, the orifice I28 beingcontrolled by a manually adjustable, spring-held screw I30 to controlthe supply of idling fuel mixture. Two orifices I32 and I34 admit air tothe passage 940 above the main fuel inlet I04.

During idling of the engine when the throttle is substantially or nearlyclosed, the high suction of the intake passage posterior to the throttleis communicated to the fuel in the passage 22 through the arrangement ofpassages described above. This will cause fuel to flow from the passage22 through the several passages above described and finally through theorifice I28 into the mixture passage to supply combustible mixture foridling purposes. A stream of solid fuel flows through the passages 22and 94 but is mixed with air which enters the orifices I32 and I34 andfrom that point to the orifice I28 a rich mixture of fuel and air isconveyed through the idling fuel passage and is discharged into theintake passage, the quantity of this idling mixture being manuallyregulated by adjustment of the valve I30. Some additional air will flowthrough the orifice I26 into the idling mixture as it is drawn throughthe passage I24, if the throttle is closed to such an extent that suchorifice is anterior to the throttle.

During idling there is practically no flow of air through the primaryVenturi tube and no introduction of fuel into such tube from the mainfuel inlet. However, as the throttle is moved toward its open positionfrom the idling position, the flow of air through the primary venturiwill be progressively increased and the suction will ultimately becomegreat enough in the main fuel inlet to effect a flow of fuel therefrom.The flow of fuel from the main inlet begins before ,the flow of idlingmixture ceases, but as the throttle is progressively opened, the suctionin the primary Venturi will become so great by com- ;parison with thesuction at the orifice I28 that flow from such orifice will cease andinstead there will be a flow from the intake passage back into theidling passage I24 through this orifice and a reverse fiow from thatpoint back through the idling mixture passages which have been describedalready, to the main fuel inlet. Thus, after the throttle has beenopened suiliciently for the suction to the main fuel inlet to becomehigh enough there will be a flow of mixture from the mixturepassagealong the path above described back to the main fuel inlet andthis mixture will pass out into the mixing chamber through the main fuelinlet along with the fuel which is supplied to such inlet from thepassage 94.

In carburetors of the prior art there have been some difficultiesencountered at the time of transfer of operation from the idle system tothe main fuel inlet due to a momentary leaning of the mixture at suchtime. This was largely due to the fact that while the idling systemfunctioned, the fuel for the main fuel inlet was maintained at anappreciable distance from such inlet so that before the main fuel inletbegan to function the fuel had to move through this distance. Due to theinertia of the fuel, this movement of fuel to the main inlet required anappreciable interval of time so that there was a slight lag in the fiowof fuel from the main inlet with respect to the fiow of air through theintake passage. In the device disclosed herein the above describeddifficulty is largely eliminated because ,a solid column of fuel whichhas not been mixed with air is maintained in the passages 22 and 94 andextends to a point immediately adjacent the main fuel inlet before itbegins functioning. Therefore, when the latter does begin to operv ate,the fuel does not have to be moved through any appreciable distance. Itis maintained at a point immediately adjacent the main inlet, thedistance through which it has to be moved when fiow from the main inletstarts being negligible.

The bleed holes I32 and I34 which admit air to the fuel passage 94aimmediately above the main fuel inlet not only supply air to mix withthe fuel in formation of the idle mixture, but also to reduce thesurface tension of the solid fuel at this point and to cause thetransfer of fuel from the idle range to the main range to bemadesmoother. The admission of air at relatively high velocity throughthe orifices I32 and I34 aids in effecting thorough atomization of thefuel which is discharged from the passage 94 to form a homogeneousmixture which is supplied to both the idling fuel passage and the mainfuel discharge inlet I04.

As the throttle moves toward open position, it will reach a positionsoon after the beginning of its opening movement where the orifice I26will lie on the posterior or high suction side of the throttle. Afterthe throttle reaches this position, the suction effective on the idlingfuel supply passages will be progressively increased and will slightlyincrease the supply of idling mixture.

Shown in Fig. 1, is a cylinder I40 in which slides a pump piston I42which is operated in response to rapid opening movements of the throttleto provide additional fuel during acceleration to enrich the mixture tosome extent as is required for best operation under such operatingconditions. Since the pump and its operating mechanism forms no part ofthe present invention, it is not completely shown and will not befurther described for the sake of simplifying the disclosure.

An unbalanced. choke valve I44 is positioned in the air inlet end of themixture passage and is secured to a shaft I46 suitably journalled in thecasting section 6. The choke valve is positioned in accordance withvariations in temperature and engine suction by mechanism positioned inthe housing I48 and which includes a thermostat I50, engaging an arm I52secured to the shaft I46, and a suction operated piston I54 engaging theopposite end of arm I52 and exerting a force to move the choke valveopen upon an increase in engine suction. Since the details of the chokevalve controlling mechanism form no part of this invention suchmechanism will not be further described.

The throttle valve shaft is operated by an arm I56 which carries anadjustable stop screw I58 adapted to engage a fast idle cam (not shown)movable to different positions by a rod I60 operated by the choke valveshaft. This mechanism causes the engine idling to be faster than normalat low temperatures to prevent stalling, but forms no part of thepresent invention.

The pump mechanism, the choke valve operating mechanism and the fastidle mechanism are all fully shown and described in application S. N.192,035 of which this application is a. division.

The subject matter claimed in this application is an improvement on andsomewhat similar to devices disclosed and claimed in co-pendingapplications to Olson, Serial No. 132,821, filed December 14, 1949, andStoltman, Serial No. 186,419, filed September 23, 1950, both of commonownership with the present application.

A vent tube I62 connects the air intake with the pump cylinder to ventthe float chamber as fully described in the parent application.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. A charge forming device for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passagehaving an air intake and a mixture outlet, a throttle valve in saidmixture passage for controlling the fiow of combustible mixturetherefrom, main and idling fuel inlets for supplying fuel to the mixturepassage, a fuel conduit for conveying fuel from the fuel supply chamberto said fuel inlets which includes a fuel conveying member extendingdownwardly into the fuel supply chamber, said member being so positionedthat it is completely surrounded by fuel in the chamber and having twofuel passages formed therein, fuel inlet means admitting fuel from thefuel supply chamber to both said fuel passages, a substantiallyhorizontal member connected with said downwardly extending member andhaving a fuel conduit formed therein, and a substantially verticalpartition in said conduit which divides the conduit into two passageseach of which is connected with one of the fuel passages in saiddownwardly extending member.

2. A charge forming device for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passagehaving an air intake and a mixture outlet, a throttle valve in saidmixture passage for controlling the fiow of combustible mixturetherefrom, main and idling fuel inlets for supplying fuel to the mixturepassage, a fuel conduit for conveying fuel from the fuel supply chamberto said fuel inlets which includes a member extending downwardly intothe fuel supply chamber and having a passage therein, a substantiallyhorizontal passage connecting with the upper end of said first-mentionedpassage, and a substantially vertical partition in said horizontalpassage and means whereby the fuel supplied by the downwardly extendingpassage is caused to flow through the horizontal passage on both sidesof said partition.

3. A charge forming device for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passagehaving an air intake and a mixture outlet, a throttle valve in saidmixture passage for controlling the flow of combustible mixturetherefrom, main and idling fuel inlets for supplying fuel to the mixturepassages, a fuel conduit for conveying fuel from the fuel supply chamberto said fuel inlets which includes a substantially horizontal passagehaving a substantially vertical partition therein, a member extendingdownwardly into the fuel supply chamber and having a passage thereinwhich communicates at its upper end with said horizontal passage at oneside of said vertical partition, and a tube extending downwardly intothe second mentioned fuel passage and communicating at its upper endwith the horizontal fuel passage at the opposite side of said partition.

4. A charge forming device for an internal combustion engine having, incombination, a constant level fuel supply chamber, an intake passagehaving an air intake and a mixture outlet, a throttle valve in saidmixture passage for controlling the fiow of combustible mixturetherefrom, main and idling fuel inlets for supplying fuel to the mixturepassage, a fuel conduit for conveying fuel from the fuel supply chamberto said fuel inlets which includes a substantially horizontal passagehaving a substantially vertical partition therein, a member extendingdown wardly into the fuel supply chamber and having a passage thereinwhich communicates at its upper end with said horizontal passage at oneside of said vertical partition, and a tube extending downwardly intothe second-mentioned fuel passage and communicating at its upper endwith the horizontal fuel passage at the opposite side of said partition,the passage through said tube being of smaller size than the passage insaid downwardly extending member at its point of connection with thehorizontal member.

5. A charge forming device for internal combustion engines having, incombination, a constant level fuel supply chamber, an intake passageprovided with an air inlet and a throttle valve for controlling the flowof combustible mixture therethrough, a main and idling fuel inlets forsupplying fuel to said intake passage, an inverted U-shaped fuel passagefor supplying fuel to said inlets, said passage having a leg extendingdownwardly into the fuel chamber and through which only fuel flows,another leg extending downwardly to supply fuel to the idling fuelinlet, a connecting passage located above the level of fuel in the fuelsupply chamber for connecting the two downwardly extending legs andsupplying fuel direct to the main fuel inlet, a substantially verticalpartition in said connecting passage dividing it into two parts, andmeans for causing fuel to be delivered from the firstmentioned leg tothe connecting passage on both sides of said partition.

ELMER OLSON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,223,987 Firth Dec. 3, 1940 2,271,114 Bracke Jan. 27, 19422,346,711 Stupecky Apr. 18, 1944

